1. Field of the Invention
This invention relates to a continuously variable automatic transmission. More particularly, the present invention relates to a hydraulic continuously variable transmission, including a swash plate plunger pump and a swash plate plunger motor connected to each other through a closed hydraulic circuit.
2. Description of the Background Art
As to hydraulic continuously variable transmissions including a hydraulic pump and a hydraulic motor in combination, a variety of forms and configurations of such transmissions have been known and put to practical use. One example of a commercial hydraulic continuously variable transmission was sold by Honda and marketed under the trademark “Hondamatic” on the 2001 Honda Fourtrax Foreman Rubicon™ TRX500 RTV.
Another example of a known hydraulic continuously variable transmission is disclosed in Japanese Patent Laid-open No. Hei 6-2753, Japanese Patent Laid-open No. Hei 6-42446, and Japanese Patent Publication No. Hei 7-88884 proposed by the present applicant. The hydraulic continuously variable transmission disclosed in these patent documents includes a swash plate plunger pump, a swash plate plunger motor, and a closed hydraulic circuit for connecting a discharge port and a suction port of the swash plate plunger pump to a suction port and a discharge port, respectively, of the swash plate plunger motor, wherein a pump swash plate member is driven by an engine, a pump cylinder and a motor cylinder are connected to each other and disposed in a connected state on an output shaft, a motor swash plate is restricted in rotation, and the motor swash plate angle can be variably adjusted.
In the hydraulic continuously variable transmission referenced above, the motor swash plate angle is variably regulated to vary the volume of the motor, thereby performing a continuously variable speed change control for steplessly varying the motor output rotation. In other words, the speed change control range (speed change ratio range) of the hydraulic continuously variable transmission is determined by the regulation range of the motor swash plate angle. Generally, the speed change control range is required to be wide, and it is necessary to widen the regulation range of the motor swash plate angle as much as possible.
In the hydraulic continuously variable transmission as disclosed in the above patent references, however, a motor swash plate (motor oscillating member) is pivotally supported by a motor casing (swash plate support member), and the output shaft, with a motor cylinder connected thereto, is rotatably supported on the motor casing through a rotatable bearing.
However, there has been the problem that an attempt to pivotally move the motor swash plate to its maximum extent leads to interference of a swash plate support member with the rotatable bearing.
In addition, in the conventional hydraulic continuously variable transmission described in the above patent references, an end portion of the swash plate support member is skewly cut, in order to obviate the interference with the rotatable bearing, and to enlarge the angle of available motion. In this case, however, the skew cutting of the end portion of the swash plate support member complicates the processing steps, leading to a rise in the component part production cost.
Although the known devices have some utility for their intended purposes, there is still a need to provide an improved hydraulic continuously variable transmission. More particularly, there is a need for an improved hydraulic continuously variable transmission including a swash plate plunger pump and a swash plate plunger motor connected to each other through a closed hydraulic circuit.